1. Field of the Invention
The present invention relates to a mobile telephone battery charger and, more specifically, to such a mobile telephone battery charger, which has means to detect and indicate the value of electric voltage or current of electric power passing through.
2. Description of the Related Art
FIG. 1 illustrates a conventional mobile telephone battery charger 1, which comprises an AC/DC adapter 11, and a cable 13 extended from one end of the AC/DC adapter 11 for connecting the AC/DC adapter 11 to a mobile telephone M. The AC/DC adapter 11 comprises a set of metal blades 12 for insertion into an electric outlet (not shown) to receive AC power supply, and a LED (light emitting diode) 14, which emits light when electric current passing through the AC/DC adapter 11. The AC/DC adapter 11 converts AC power supply into DC power supply for charging the battery of the mobile telephone M connected to the cable 13. This design of mobile telephone battery charger is still not satisfactory in function. After a long use of the mobile telephone battery charger, the internal electronic component parts of the AC/DC adapter 11 may be damaged or not functioning well. In this case, the output voltage of the AC/DC adapter 11 differs from the rated value, for example, changed from 3.8V to 4.2V or 4.5V. Charging the battery of a mobile telephone M with a higher voltage than the rated value may affect the functioning of the battery or the internal charging circuit of the mobile telephone and shorten their service life. Further, when charging the battery of a mobile telephone M, the power level indication block shown on the display screen of the mobile telephone M is simply a rough indication that does not accurately tells the value of the power level of the battery. Excessively charging the battery may shorten its service life, or cause damage to it.
The present invention has been accomplished to provide a mobile telephone battery charger, which eliminates the aforesaid problems. It is one object of the present invention to provide a mobile telephone battery charger, which indicates the voltage value of the charging power before charging the battery, preventing an abnormal charging of charging the battery with wrong voltage. It is another object of the present invention to provide a mobile telephone battery charger, which indicates the current value of the charging power when charging the battery, enabling the user to know the power storage status of the battery. To achieve these and other objects of the present invention, the mobile battery charger comprises a LCD, a selector switch, and a microprocessor controlled by the selector switch to drive the LCD to indicate the voltage value or current value of output charging electricity. Before charging the battery, the selector switch is switched to the voltage indication position to drive the microprocessor to indicate the voltage value of the output charging electricity through the LCD, preventing an error charging action to damage the battery of the mobile telephone. During charging, the selector switch is switched to the current indication position to drive the microprocessor to indicate the current value of the output charging electricity through the LCD. By means of the variation speed of the indication of current value to zero reading, the user knows the power storage ability of the battery of the mobile telephone been charged.